Research Projects

The staff that works for Indiana

The Survey consists of a diverse group of scientists, specialists,
and support staff dedicated to serving the earth science needs of
the state of Indiana. They include research geologists in a variety
of disciplines and specialists in cartography, GIS, database and web
development, editing, and layout design, supported by an active
business staff. The Survey is organized into three divisions:
Research, Information Services, and Business Affairs.

Geological Hazards

IGSMap is the public source for geologic maps and data in Indiana.
The Map Gallery helps people find commonly used maps and information
for a better understanding of Indiana's geologic materials, resources,
and issues.
View IGSMap Gallery

Online Services

Offline Services

In geology there are two main uses to which fossils are put.
These are biostratigraphic correlation and environmental interpretation.
Before discussing these two points, I should say that these two utilities of fossils are
not necessarily those that are most interesting to a paleontologist who studies fossils.
Evolutionary studies are important because of the light they shed on the mechanism of
evolution and the interaction between evolution and extinction, not necessarily because
evolution indirectly provides a powerful tool for matching up rocks of the same age but of
different composition in widely separated areas. Deciphering ancient environments is
important, but the paleontologist is concerned with the ancient communities of life that
once inhabited those environments, about the interactions, competition, and predation
among members of the community, and how food supplies are gathered, partitioned, and
utilized by community members.

Biostratigraphic Correlation

The matching up of rocks of the same age from place to place is called correlation
of the rock layers. If a particular rock layer was deposited continuously over an area,
correlation can be done by physically matching the rock layer from place to place. Thus, a
brown, 5-foot-thick limestone, with chert nodules, an upper wavy surface and a lower
planar surface can be recognized by this association of physical characters. Wherever this
limestone layer crops out at the earth's surface, you can say "Aha, this is the same
layer as I saw at such-and-such a place!" This kind of correlation is restricted to
the area where that specific rock layer was deposited.

However, suppose I collect a bunch of fossils from that rock layer near Bloomington,
and I think that the bed is about the same age as some rocks in Missouri. Obviously I
cannot directly trace the bed that far, because it wasn't deposited over that long
distance. Instead, by studying the fossils I can determine which rock unit in Missouri
contains the closest match of the species of fossils I have found in Indiana. This
indicates that the greatest proportion of species were alive at the same time in Indiana
and Missouri, and that the rock layer in Missouri that contains these fossils is very
close to, or the same age, as the rock layer in Indiana.

Use of fossils in this way, to determine the relative ages of rocks, is ultimately
based on evolution. Through time, new species have appeared and older species have become
extinct. Thus, the species that are alive at one time are somewhat different from those
that are alive before or after that time. This results in a succession of fossil types
through ages of rocks. This is called faunal succession as applied to animals,
or floral succession for plant fossils. Using this principle we can correlate rocks between
Indiana, for instance, and rocks of the same age all over the earth--because they contain
the same fossils.

Some fossils are much more useful for this practice than are others. It helps if the
particular group of organisms, whatever they are, is evolving rapidly. Thus, more species
useful for discriminating small periods of time occur more closely spaced in the rocks. It
also helps if the organism has wide latitude in where it can live. For instance, if a clam
can only live in sand, its fossil shells will only be found in sandstone, and it won't be
of much use at all in trying to correlate a sandstone with a limestone. For this reason,
organisms that did not live on the sea floor and were controlled by the nature of the sea
bottom are most useful. Creatures that swam or floated up in the sea water were
independent of bottom conditions and are also prone to be distributed over wide areas,
perhaps even having worldwide distribution. These, if they evolved rapidly, make ideal
fossils for correlation.

Environmental Interpretation

Suppose you find a thick layer of sandstone. You study the texture--size of the sand
grains, rounding, sorting, the mineral composition of the sand grains. From all this you
can determine the agent of transport, whether the sand was deposited in water, and so on.
But, you now go on and ask--Was this sandstone deposited in the ocean or in fresh water?
An obvious and important question. One of the best and surest ways to get a satisfactory
answer to this question is to find some fossils. These will tell you much about the
environment in which the rock was deposited because different kinds of plants and animals
were confined to specific environments, just as they are today--another example
of uniformitarianism. If you find fossil brachiopods, bryozoans, and echinoderms, the rock
was surely deposited in the ocean. Here are some simple generalities that will aid in making
environmental interpretations of fossils. You should realize that these are not 100% perfect.
There are exceptions. But these rules will work about 95% of the time:

A rock with plant fossils (leaves, stems, etc) and with fossil bones, is almost
certainly laid down on land or in fresh water. An exception is fish bones--these may be
either freshwater or marine, but bones of mammals, reptiles, and so on are usually
preserved on dry land.

Any rock with lots of shells--brachiopod, snail, clam, bryozoans, sponges, corals,
cephalopods, etc. was surely deposited in the oceans. We can distinguish two or three
sub-environments for the marine condition.

Thin-shelled fossils are more common in deep water than they are in shallow water.
Conversely, thick-shelled fossils are more common in shallow water than they are in deep
water. Thus, in marine environments you can sometimes distinguish deep from shallow water.

Fossil graptolites are usually in fine-grained dark shales that were deposited in deep
water.

Colonies of corals are typically associated with coral reefs, all of which grew in
shallow water.

Algae or seaweed that lived in the oceans would be found in shallow water rocks, because
these are photosynthetic and need sunlight to flourish.